diff --git a/src/d2_docker/commands/create.py b/src/d2_docker/commands/create.py
index e06fa15..4352875 100644
--- a/src/d2_docker/commands/create.py
+++ b/src/d2_docker/commands/create.py
@@ -46,26 +46,8 @@ def create_core(args):
 
 def get_core_build_dir(args):
     base_dir = utils.get_docker_directory("core", args)
-    major_version = get_major_version(args.version or args.war)
-    utils.logger.info("DHIS2 major version: {}".format(major_version or "-"))
-
-    if not major_version:
-        raise utils.D2DockerError("Cannot get version from --version or --war")
-    else:
-        if major_version >= 42:
-            return os.path.join(base_dir, "java-17-tomcat-10")
-        elif major_version >= 41:
-            return os.path.join(base_dir, "java-17")
-        else:
-            return os.path.join(base_dir, "java-11")
-
-
-def get_major_version(s):
-    """Return major DHIS2 version. Ex: "2.38.4" -> "38". "40.1.2" -> 40."""
-    match = re.search(r"(\d+\.\d+)", s)
-    if not match: return None
-    parts = [int(s) for s in match.groups()[0].split(".")]
-    return parts[1] if parts[0] == 2 else parts[0]
+    major_version = utils.get_major_version(args.version or args.war)
+    return utils.get_core_java_dir(base_dir, major_version)
 
 
 def create_data(args):
diff --git a/src/d2_docker/commands/upgrade.py b/src/d2_docker/commands/upgrade.py
index aaac7f2..fffa8df 100644
--- a/src/d2_docker/commands/upgrade.py
+++ b/src/d2_docker/commands/upgrade.py
@@ -68,7 +68,7 @@ def upgrade_to_version(
     )
     war_exists = dhis_war_path and os.path.exists(dhis_war_path)
     create_core_kwargs = dict(war=dhis_war_path) if war_exists else dict(version=version)
-    core_docker_dir = utils.get_docker_directory("core")
+    core_docker_dir = utils.get_core_java_dir(utils.get_docker_directory("core"), utils.get_major_version(version))
     utils.create_core(
         docker_dir=core_docker_dir,
         image=core_image,
diff --git a/src/d2_docker/utils.py b/src/d2_docker/utils.py
index 0442a6c..8f94765 100644
--- a/src/d2_docker/utils.py
+++ b/src/d2_docker/utils.py
@@ -68,6 +68,28 @@ def copytree(source, dest):
     dir_util.copy_tree(source, dest)
 
 
+def get_core_java_dir(base_dir, major_version):
+    logger.info("DHIS2 major version: {}".format(major_version or "-"))
+
+    if not major_version:
+        raise D2DockerError("Cannot get version from --version or --war")
+    else:
+        if major_version >= 42:
+            return os.path.join(base_dir, "java-17-tomcat-10")
+        elif major_version >= 41:
+            return os.path.join(base_dir, "java-17")
+        else:
+            return os.path.join(base_dir, "java-11")
+        
+
+def get_major_version(s):
+    """Return major DHIS2 version. Ex: "2.38.4" -> "38". "40.1.2" -> 40."""
+    match = re.search(r"(\d+\.\d+)", s)
+    if not match: return None
+    parts = [int(s) for s in match.groups()[0].split(".")]
+    return parts[1] if parts[0] == 2 else parts[0]
+
+
 def run(
     command_parts,
     raise_on_error=True,
@@ -606,6 +628,9 @@ def wait_for_server(port):
     url = "http://localhost:{}".format(port)
 
     while True:
+        # This functions is called right after a "docker up", which takes a little to be able to start the nginx (and way longer for the tomcat to be ready),
+        # so to avoid calling before nginx can accept connections (and raising an exception) just move the sleep to be the first step
+        time.sleep(5)
         try:
             logger.debug("wait_for_server:url={}".format(url))
             urllib.request.urlopen(url)  # nosec
@@ -619,7 +644,6 @@ def wait_for_server(port):
         except urllib.request.URLError as exc:
             logger.debug("wait_for_server:url-error: {}".format(exc.reason))
 
-        time.sleep(5)
 
 
 def create_core(